YOU SAID:

When I go back in to the future, the past is left back

INTO JAPANESE

未来に戻ると、過去は後ろに残る

BACK INTO ENGLISH

Back to the future, the past will stay behind

INTO JAPANESE

未来に戻って、過去は後ろにとどまるだろう

BACK INTO ENGLISH

Back to the future, the past will stay behind